1. The Field of the Invention
The present invention relates to insulative connectors used in the formation of composite wall structures that include an insulating layer and at least one adjacent structural layer. In particular, the present invention relates to connectors for maintaining the forms used to form the wall structures in a fixed position during manufacture and for thereafter securing together the insulating and structural layers after removal of the forms.
2. Relevant Technology
As new materials and compositions have been developed, apparently unrelated materials have been synergistically combined to form useful composite materials. One such example is seen in the area of building and construction, in which high strength structural walls have been coated and layered with highly insulative materials which generally have relatively low structural strength. The resulting composite wall structure has high strength and is highly insulative. Conventionally, the structural component of such as a wall is built first, after which the insulating layer or sheet is attached to the structural component. Thereafter a protective cover is placed over the insulating material to protect and hide it. The insulating barrier reduces the transfer of thermal energy across the composite wall structure.
Concrete is one of the least expensive and strongest materials commonly used in the construction industry. Unfortunately, concrete, which is a mixture of hydraulic cement, water, and an aggregate such as rocks, pebbles, and sand, offers relatively poor insulation compared to many other materials. For example, a slab of concrete having an 8 inch thickness has an R value of about 0.64, while a one-inch thick panel of polystyrene has an R value of about 5.0. The R value of a material is proportional to the thermal resistance of the material and is useful for comparing the insulating properties of materials used in the construction industry.
In contrast with concrete, highly insulative materials, at least those of reasonable cost, typically offer poor structural strength and integrity. While lightweight aggregates having higher insulating ability may be incorporated within concrete to increase the insulating effect thereof, the use of such aggregates in an amount that has a dramatic effect on the insulation ability of the concrete will usually result in greatly decreased strength of the resulting structure.
It has been found that positioning at least one concrete layer adjacent to at least one insulating layer provides a composite wall structure that has both good insulating capability and good structural strength. One strategy for forming these composite wall structures is to position an insulating layer between two concrete layers. This technique, however, poses the risk of allowing the two concrete layers to collapse together or to separate apart during construction or subsequent use of the building. Accordingly, it is necessary to structurally bridge or connect the two concrete layers together. This is conventionally accomplished by using metal studs, bolts, beams, or other connecting devices.
Because metal readily conducts thermal energy, metal studs, bolts, and beams that are used to structurally bridge a pair of structural layers have the effect of significantly reducing the insulating properties of a composite wall. In particular, such metal studs, bolts, or beams provide channels through which thermal energy may be conducted. This is true even though the metal connecting devices may be surrounded by ample amounts of insulating material. Composite wall structures that use metal connecting devices do not prevent heat from flowing from a relatively warm inside wall to a colder outside wall during cold weather, for example, as effectively as composite walls that do not use metal connecting devices. Of course one might construct a building having no structural bridges between the inner and outer structural walls, although the result would be a building having inadequate stability for most needs.
In order to reduce thermal bridging, some have employed connector devices having a metal portion that passes through the concrete layers and a thermally insulating portion that passes through the insulating layer, e.g., U.S. Pat. No. 4,545,163 to Asselin. Others have developed connector devices made entirely from polymeric or other highly insulative materials. Examples of the foregoing include U.S. Pat. No. 4,829,733 to long; U.S. Pat. No. 5,519,973 to Keith et al.; U.S. Pat. No. 5,606,832 to Keith et al.; and U.S. Pat. No. 5,673,525 to Keith et al. For purposes of disclosing insulating connector devices used to secure a composite wall structure together, each of the foregoing patents are incorporated herein by specific reference.
A common technique for forming composite wall structures is known in the art as the "cast-in-place" method, wherein the wall is formed within vertically positioned forms that are erected at or near the location where the composite wall structure is to be finally positioned. In the cast-in-place method the forms and insulating layer are first positioned vertically, after which concrete or other structural material is poured into the spaces between the insulating layer and forms. Connector devices having a length that is equal to or less than the width of the composite wall structure arc placed substantially orthogonally through a vertically oriented insulating layer, with the ends of the connector devices extending out of either surface of the insulating layer. Connectors that are especially useful in manufacturing composite wall structures according to the cast-in-place method are disclosed in the aforementioned U.S. Pat. No. 5,673,525 to Keith et al. Such connectors assist in maintaining the insulating layer at a desired orientation or spacing relative to the forms. This is accomplished by the connector ends making abutment with the inner surfaces of the forms and by means of flanges or other orienting means for maintaining the insulating layer at a desired distance from either of the connector ends. Although the connectors of Keith et al. '525 provide superior benefits as described therein, other connectors, such as those disclosed in U.S. Pat. No. 4,829,733 to Long, could be used in the cast-in-place method.
Existing insulating connector devices used in conventional cast-in-place methods prevent collapse of the forms toward the insulating layer, but do not restrain the forms from moving away from the insulating layer. In order to prevent outward lateral movement of the forms away from the insulating layer, lateral supporting structures such as buttresses and braces must be used. Buttresses and braces can offset the outwardly pushing forces of the freshly poured concrete material against the forms and maintain the forms in a rigid, spaced-apart orientation. However, the use of lateral support structures is time consuming and requires the transport and storage of the relatively heavy and bulky support structures every time a job is begun or completed.
In view of the foregoing, there exists a need for connector devices capable of rigidly restraining motion of forms used in the cast-in-place method in a direction away from the insulating layer and which are small and lightweight compared to conventional lateral support structures.
It would also be an improvement if such connectors included additional features that prevented collapse of the forms toward the insulating layer, particularly prior to filling the spaces between the forms and insulating layer with structural material.
It would be a further advancement in the art if such connector devices for restraining motion of the forms also served the dual purpose of securing the composite wall structure together upon hardening of the structural layers.
The foregoing form-restraining connector devices would be particularly desirable if they were themselves highly insulative in order to not create a thermal bridge between the structural layers.
There is also a need for such form-restraining connector devices that could be manufactured at a relatively low cost per unit.
Such devices for restraining lateral movement of forms during the formation of composite wall structures are disclosed and claimed herein.